Light-emitting glass, light-emitting device equipped with the light-emitting glass, and process for producing light-emitting glass

ABSTRACT

Provided is a light-emitting glass which is applicable to, e.g., white illuminators including a light-emitting diode as a light source, and which emits light of a warm white color when irradiated with near ultraviolet light and combines long-term weatherability with high heat resistance. Also provided are a light-emitting device equipped with the light-emitting glass and a process for producing the light-emitting glass. The light-emitting glass includes, as the base glass, borosilicate or silicate glass having a separated-phase structure, whereby the base glass is efficiently doped with, for example, transition metal ion clusters which emit light of a warm white color upon irradiation with near ultraviolet light. With this glass, it is possible to attain increases in excitation wavelength and emission wavelength. The glass thus emits, based on a multiple scattering effect, high-intensity light of a warm white color upon irradiation with near ultraviolet light. Furthermore, since the light-emitting glass includes borosilicate or silicate glass, which is a common glass material, as the constituent material, it is possible to inexpensively provide a fluorescent material combining long-term weatherability with respect to ultraviolet rays, etc. with resistance to high temperatures.

TECHNICAL FIELD

The present invention relates to a light-emitting glass, alight-emitting device equipped with the light-emitting glass, and aprocess for producing the light-emitting glass. More specifically, thepresent invention relates to a light-emitting glass which emits light ofa warm white color (yellow to orange) when irradiated withnear-ultraviolet light, a light-emitting device equipped with thelight-emitting glass, and a process for producing the light-emittingglass.

BACKGROUND ART

In recent years, fluorescent materials for light-emitting devices usedfor flat panel displays, high-intensity and low-power consumptionlighting, etc. have gained much attention. In regard to such fluorescentmaterials, development of fluorescent materials or light-emittingmaterials with less environmental load and free from rare raw materialsother than fluorescent lamps using mercury or fluorescent materialscontaining much rare earths has been required in view of globalenvironmental problems. Furthermore, since high color renderingproperties are needed for illumination light sources, the illuminationlight sources have also been required to have a broad spectrum within adesired wavelength region (color gamut) in a visible light range ofabout 400 nm to 800 nm in wavelength. In this kind of environment, whitelight-emitting diodes (LED) or light-emitting devices equipped with themhave been attracting attention as new illumination light sources inplace of fluorescent lamps or incandescent lamps. Illumination using alight source of white light-emitting diodes closer to practical useprovides advantages of high luminance efficiency and longer operatinglife; therefore, such illumination light sources are expected to bepromising in the future.

There are the following configurations in the white light-emittingdiodes: (a) purple to blue light-emitting diodes plus yellowlight-emitting phosphor fine particles, (b) ultraviolet light-emittingdiodes plus various phosphor fine particles of RGB light-emitting type,and (c) RGB three-color light-emitting diodes; among these, theconfiguration (a) has become mainstream and is exemplified by acombination of a blue light-emitting diode and a YAG:Ce fluorescencesubstance, in which cerium (Ce) of an activator is introduced intoyttrium aluminate (Y₃Al₅O₁₂: YAG) of a base material of fluorescencesubstance to thereby exhibit blue color rendering (e.g., see PatentDocument 1). Furthermore, a glass matrix, into which a transition metalion has been introduced, causes light absorption in a visible lightregion or fluorescent emission in a near-infrared region and thus can beused as a fluorescent substance through the use of a high intensityemission. There has been provided a glass material containing amonovalent copper ion (Cu⁺ ion) and exhibiting blue fluorescence as sucha fluorescent substance (e.g., see Patent Document 2).

-   Patent Document 1: Japanese Unexamined Patent Application,    Publication No. H10-36835-   Patent Document 2: Japanese Unexamined Patent Application,    Publication No. H10-236843

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

As explained above, there has been a problem that current whitelight-emitting diodes exhibit blue color rendering, however, provide acool feeling in emission color due to stronger blue and weaker red sincethe color rendering range required of light-emitting diodes for generallighting is warm (yellow to orange). There has also been a problem thathigh-power light-emitting diodes are necessary for increasingillumination intensity, however, the high-power light-emitting diodeslead to higher heat generation and thus resins or fluorescent materialsthemselves degrade due to high temperatures resulting from the heatgeneration.

The present invention has been made in view of the problems describedabove; and it is an object of the present invention to provide alight-emitting glass which is applicable to white illuminators includinga light-emitting diode as a light source, emits light of a warm whitecolor when irradiated with near ultraviolet light, and combineslong-term weatherability with high heat resistance; a light-emittingdevice equipped with the light-emitting glass, and a process forproducing the light-emitting glass.

Means for Solving the Problems

In order to solve the problems described above, in a first aspect of thepresent invention, there is provided a light-emitting glass whichincludes a borosilicate glass having a separated-phase structurecomposed of at least one of (i) to (iii) below as a base glass, in whichthe base glass includes a transition metal ion cluster and/or transitionmetal cluster containing at least one selected from the group consistingof copper (Cu), gold (Au), and silver (Ag) as a constituent metal;

(i) alkali metal borosilicate glass having a separated-phase structure(R₂O—B₂O₃—SiO₂),

(ii) alkali earth metal borosilicate glass having a separated-phasestructure (R′O—B₂O₃—SiO₂), and

(iii) alkali metal-alkali earth metal borosilicate glass having aseparated-phase structure (R₂O—R′O—B₂O₃—SiO₂);

in (i) to (iii), R represents an alkali metal and R′ represents analkali earth metal, respectively.

In a second aspect of the present invention, there is provided alight-emitting glass which includes a silicate glass having aseparated-phase structure composed of at least one of (iv) to (vi) belowas a base glass, in which the base glass includes a transition metal ioncluster and/or transition metal cluster containing at least one selectedfrom the group consisting of copper (Cu), gold (Au), and silver (Ag) asa constituent metal;

(iv) alkali metal silicate glass having a separated-phase structure(R₂O—SiO₂),

(v) alkali earth metal silicate glass having a separated-phase structure(R′O—SiO₂), and

(vi) alkali metal-alkali earth metal silicate glass having aseparated-phase structure (R₂O—R′O—SiO₂);

in (iv) to (vi), R represents an alkali metal and R′ represents analkali earth metal, respectively.

According to a third aspect of the present invention, in thelight-emitting glass described above, the transition metal ion clusteris a copper ion cluster (Cu⁺ cluster), and the base glass is an alkalimetal borosilicate glass having a separated-phase structure(R₂O—B₂O₃—SiO₂).

According to a fourth aspect of the present invention, in thelight-emitting glass described above, the alkali metal of the alkalimetal borosilicate glass is sodium (Na).

In a fifth aspect of the present invention, there is provided alight-emitting device which includes the light-emitting glass of thepresent invention described above and a light-emitting element as alight-emitting source.

According to a sixth aspect of the present invention, in thelight-emitting device of the present invention described above, thelight-emitting element is a light-emitting diode.

In a seventh aspect of the present invention, there is provided aprocess for producing the light-emitting glass according to the firstaspect, in which a raw material component containing a compound whichcorresponds to a borosilicate glass having a separated-phase structurecomposed of at least one of (i) to (iii) for forming a base glass and acompound containing a transition metal which corresponds to thetransition metal ion cluster and/or transition metal cluster aredry-mixed, melted, and quenched.

In an eighth aspect of the present invention, there is provided aprocess for producing the light-emitting glass according to the secondaspect, in which a raw material component containing a compound whichcorresponds to a silicate glass having a separated-phase structurecomposed of at least one of (iv) to (vi) for forming a base glass and acompound containing a transition metal which corresponds to thetransition metal ion cluster and/or transition metal cluster aredry-mixed, melted, and quenched.

According to a ninth aspect of the present invention, in the process forproducing the light-emitting glass described above, tin oxide (SnO) isfurther included as a reducing agent.

According to a tenth aspect of the present invention, in the process forproducing the light-emitting glass described above, an additive amountof the tin oxide (SnO) is 0.1 to 10.0 mol % as outer percentage.

EFFECTS OF THE INVENTION

The light-emitting glass of the present invention includes theborosilicate or silicate glass having a separated-phase structure as abase glass, whereby the base glass is efficiently doped with, forexample, the transition metal ion cluster or transition metal clusterwhich emits light of a warm white color (yellow to orange) whenirradiated with near-ultraviolet light, thus achieving to increaseexcitation wavelength and emission wavelength and resulting in afluorescent material which emits high-intensity light of a warm whitecolor (yellow to orange) upon irradiation with near ultraviolet lightdue to a multiple scattering effect. Furthermore, since the borosilicateor silicate glass, which is a common glass material, is included as theconstituent material, it is possible to inexpensively provide afluorescent material combining long-term weatherability with respect toultraviolet rays, etc. with resistance to high temperatures.

The light-emitting device of the present invention is equipped with thelight-emitting glass of the present invention and a light-emittingelement as a light-emitting source; therefore, the light-emitting deviceemits high-intensity light of a warm white color (yellow to orange) andis excellent in weatherability and heat resistance and thus may complywith saving of energy in place of incandescent lights or fluorescentlamps and saving of rare resources.

In the process for producing the light-emitting glass of the presentinvention, a raw material component containing a compound whichcorresponds to a borosilicate glass or silicate glass for forming a baseglass and a compound containing a transition metal which corresponds tothe transition metal ion cluster etc. is dry-mixed and vitrified bymelting and quenching, therefore, the light-emitting glass capable ofexerting the effects described above can be simply produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a phase diagram of NBS (Na₂O—B₂O₃—SiO₂) system;

FIG. 2 is a schematic view showing an embodiment of the light-emittingdevice of the present invention;

FIG. 3 is a graph showing an absorption spectrum of the case where tinoxide is added as a reducing agent in Evaluation (1);

FIG. 4 is a view showing appearance photographs of glass samples whichare irradiated with white light or ultraviolet light having a centralwavelength of 254 nm or 365 nm in Evaluation (1);

FIG. 5 is a graph showing an excitation spectrum and an emissionspectrum of a glass sample in Evaluation (1);

FIG. 6 is a graph showing a relation between a glass composition and anabsorption spectrum in Evaluation (2);

FIG. 7 is a view showing appearance photographs of glass samples whichare irradiated with white light or ultraviolet light having a centralwavelength of 254 nm or 365 nm in Evaluation (2);

FIG. 8 is a graph showing a relation between a glass composition, anexcitation spectrum, and an emission spectrum in Evaluation (2);

FIG. 9 is a view showing appearance photographs of glass samples inExample 1 which are irradiated with white light or ultraviolet lighthaving a central wavelength of 254 nm or 365 nm in Evaluation (3);

FIG. 10 is a view showing appearance photographs of glass samples inExample 2 which are irradiated with white light or ultraviolet lighthaving a central wavelength of 254 nm or 365 nm in Evaluation (3);

FIG. 11 is a graph showing a relation of an emission intensity(intensity of yellow emission) versus an additive amount of copper oxidein Evaluation (3);

FIG. 12 is a graph, with respect to a composition of Example 1, showingfluorescence spectra under excitation by near-ultraviolet light ofwavelength 365 nm and excitation spectra where a maximum emissionwavelength is a monitor wavelength;

FIG. 13 is a graph, with respect to a composition of Example 2, showingfluorescence spectra under excitation by near-ultraviolet light ofwavelength 365 nm and excitation spectra where a maximum emissionwavelength is a monitor wavelength;

FIG. 14 is a graph, with respect to a composition of Example 3, showingfluorescence spectra under excitation by near-ultraviolet light ofwavelength 365 nm and excitation spectra where a maximum emissionwavelength is a monitor wavelength;

FIG. 15 is a graph showing fluorescence spectra under excitation bynear-ultraviolet light of wavelength 365 nm in Evaluation (5);

FIG. 16 is a graph showing fluorescence spectra under excitation bynear-ultraviolet light of wavelength 254 nm in Evaluation (5);

FIG. 17 is a graph showing a relation between copper oxide (Cu₂O) addedand emission intensity in Evaluation (5);

FIG. 18 is a graph showing fluorescence spectra under excitation bynear-ultraviolet light of wavelength 365 nm in Evaluation (6);

FIG. 19 is a graph showing fluorescence spectra under excitation byultraviolet light of wavelength 254 nm in Evaluation (6);

FIG. 20 is a graph showing fluorescence spectra under excitation bynear-ultraviolet light of wavelength 365 nm in Evaluation (7);

FIG. 21 is a graph showing fluorescence spectra under excitation byultraviolet light of wavelength 254 nm in Evaluation (7);

FIG. 22 is a graph showing a relation between tin oxide (SnO) added andemission intensity in Evaluation (7);

FIG. 23 is a graph showing fluorescence spectra under excitation bynear-ultraviolet light of wavelength 365 nm in Evaluation (8);

FIG. 24 is a graph showing fluorescence spectra under excitation byultraviolet light of wavelength 254 nm in Evaluation (8);

FIG. 25 is a graph showing fluorescence spectra under excitation bynear-ultraviolet light of wavelength 365 nm in Evaluation (9); and

FIG. 26 is a graph showing fluorescence spectra under excitation byultraviolet light of wavelength 254 nm in Evaluation (9).

EXPLANATION OF REFERENCE NUMERALS

-   -   1: light-emitting device    -   11: light-emitting glass    -   12: light-emitting element    -   14: submount element

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention is explained. Theessential constitution of the light-emitting glass of the presentinvention is that the borosilicate glass or silicate glass having aseparated-phase structure is a base glass and the base glass contains atransition metal ion cluster and/or transition metal cluster.

(1) Transition Metal Cluster and/or Transition Metal Ion Cluster:

In the light-emitting glass of the present invention, the base glassdescribed later contains a transition metal ion cluster or transitionmetal cluster. The metal or metal ion of the transition metal ioncluster or transition metal cluster (hereinafter, sometimes referred toas “transition metal ion cluster, etc.”) is exemplified by copper (Cu),gold (Au), and silver (Ag) which are supposed to emit light in a glass;and at least one of them may be used. Among these, copper (Cu) ispreferably used since it is relatively inexpensive and the clusterthereof stably produces yellow to orange emission.

In addition, the above-mentioned transition metal ion cluster ortransition metal cluster is exemplified by copper cluster (Cu cluster),copper ion cluster (Cu⁺ cluster), gold cluster (Au cluster), gold ioncluster (Au^(n+) cluster; n: an integer of 1 to 6), silver cluster (Agcluster), silver ion cluster (Ag⁺ cluster), etc.

The term “transition metal ion cluster” or “transition metal cluster” inthe present invention means an aggregation of transition metal atoms ortransition metal ions, and the transition metal ion cluster ortransition metal cluster is incorporated into a glass material of basebody (base glass in the present invention) to form an emission centerand exhibits yellow emission as an activator. In the case of copper ioncluster (Cu⁺ cluster), for example, yellow to orange emission isexhibited at around 580 nm under excitation by ultraviolet light at along wavelength around 350 nm (e.g., 365 nm).

(2) Base Glass:

It is necessary that the base glass of the light-emitting glass of thepresent invention is a glass material having a separated-phasestructure; specifically, usable glass materials may be exemplified byalkali metal borosilicate glass having a separated-phase structure(R₂O—B₂O₃—SiO₂), alkali earth metal borosilicate glass having aseparated-phase structure (R′O—B₂O₃—SiO₂), alkali metal-alkali earthmetal borosilicate glass having a separated-phase structure (R₂₀—R′O—B₂O₃—SiO₂), alkali metal silicate glass having a separated-phasestructure (R₂O—SiO₂), alkali earth metal silicate glass having aseparated-phase structure (R′O—SiO₂), and alkali metal-alkali earthmetal silicate glass having a separated-phase structure (R₂₀—R′O—SiO₂).These borosilicate glasses or silicate glasses are materials havinglong-term weatherability to ultraviolet rays, etc. as well as high heatresistance, thus may be used without problems even in cases wherehigh-power light-emitting diodes are light sources thereof.

In the base glass, R is an alkali metal and preferably Li, Na, or K inparticular. R′ is an alkali earth metal and preferably Ca, Mg, Sr, or Bain particular. R or R′ may be selected as one kind of metal (element) ora combination of alkali metals (e.g., Na—K), alkali earth metals (e.g.,Ca—Mg), or an alkali metal and an alkali earth metal (e.g., Na—Ca),respectively. Additionally, when copper ion cluster (Cu⁺ cluster) isused as the transition metal ion cluster, the base glass is preferablythe alkali metal borosilicate glass having a separated-phase structure(R₂O—B₂O₃—SiO₂) by reason of higher efficiency of yellow to orangeemission, etc., and particularly preferably the borosilicate glass(Na₂O—B₂O₃—SiO₂) in which alkali metal of the alkali metal borosilicateglass is sodium (Na).

Here, the glass material having a separated-phase structure indicates aglass which is formed of a separated-phase texture or composed of animmiscible-region texture; for example, there exists an immiscibleregion which separates into two phases at a liquidus temperature orlower in many compositional systems containing silica or boric acidamong oxide glass systems. There exists a uniform liquid phase atcertain high temperatures in such systems, therefore, an apparentlyuniform glass may be obtained if quench is performed at thetemperatures. However, the glass is potentially likely to be immiscibleand thus generates phase separation when maintained at a temperaturewhere diffusion migration of substances is possible; therefore, thephase separation is referred to as metastable-immiscibility, and whenthe glass is heat-treated under the metastable-immiscibility at certaincomposition and temperature within a nucleation-growth mechanism region,a droplet-state separated-phase structure (separated-phase texture) isformed and a three-dimensionally intertwined separated-phase texture isalso formed at a spinodal decomposition region.

Furthermore, in regards to silicate or borate systems, two-phaseseparation often occurs at a temperature region from a liquidus tohigher temperatures, i.e. under a high-temperature melt state. Suchphase separation is referred to as stable-immiscibility, and the phaseseparation easily progresses under the melt state due to a higherdiffusion speed. In the two-component system of R′O—SiO₂ (R′: alkaliearth metal) which is a representative composition exhibiting thestable-immiscibility, generally, the stable-immiscible region extendsover a temperature region from a liquidus near 1700° C. to highertemperatures. As the size of alkali earth ion becomes larger, theseparated-phase range becomes narrower and the temperature regionbecomes lower; for example, in a case of Ba, the immiscible regioncorresponds to temperatures lower than the liquidus, i.e. to ametastable state. Additionally, the “glass having a separated-phasestructure” in the present invention indicates entirely glass materialswhere a separated-phase structure can be formed and encompasses glassmaterials where phase separation is potentially progressing even whenthe separated-phase structure is not apparently formed yet.

In general, when a metal ion of transition metal ion etc. (or metal oftransition metal) is doped in a glass material, metal ion or metalcolloid is formed in addition to metal ion cluster or metal cluster; andwhen a dope amount is excessively increased in order to increase themetal ion cluster etc., metal ion, metal colloid, etc. other than themetal ion cluster, etc. are inevitably formed since the control of metalvalence is difficult. On the other hand, when a metal ion or metal isdoped in a glass material having a separated-phase structure(borosilicate glass or silicate glass), for example, when aseparated-phase glass of silicate system is used, a metal ion (e.g., Cu⁺ion) selectively enters into a silica-poor glass phase (Na₂O—B₂O₃ richphase in NBS (Na₂O—B₂O₃—SiO₂) system), thus the metal ion (or metal) ismore easily collected and condensed into a glass phase than the case ofuniform glass; therefore, no more than a small additive amount of themetal is necessary for forming the metal ion cluster or metal cluster,thereby resulting in easy control of metal valence corresponding to thecluster and also prevention of agglomeration of metal itself;consequently, the metal ion cluster (Cu⁺ cluster in a case of copper)can be effectively formed and the light-emitting glass, which emitslight of a warm white color (yellow to orange) when irradiated withnear-ultraviolet light, can be simply obtained. In addition, by way ofdoping a transition metal ion cluster, etc. into the glass materialhaving a separated-phase structure as a fluorescent activator, a glassmaterial can be prepared that emits highly bright light due to multiplescattering at interfaces in the separated-phase structure bynear-ultraviolet light as excitation light of the fluorescent activatorand is highly resistant to ultraviolet rays, electron beam, andchemicals. Additionally, the means of confirming the separated-phasestructure in the glass material is exemplified by observation of textureusing electron microscopes, small-angle X-ray scattering processes,ultraviolet-visible light scattering processes, etc.

The composition of the glass material having the separated-phasestructure can be easily selected based on a phase diagram correspondingto the glass material. FIG. 1 shows a phase diagram of NBS(Na₂O—B₂O₃—SiO₂) system. The phase diagram of NBS system shown by FIG. 1may also be applied to alkali metal borosilicate glasses using otheralkali metals (Li, K).

In addition to the above-mentioned descriptions, with respect to thecompositions of alkali earth metal borosilicate glass having aseparated-phase structure, alkali metal-alkali earth metal borosilicateglass having a separated-phase structure, alkali metal silicate glasshaving a separated-phase structure, alkali earth metal silicate glasshaving a separated-phase structure, and alkali metal-alkali earth metalsilicate glass having a separated-phase structure, for example,composition (phase) diagrams of the separated-phase structure of NBS(Na₂O—B₂O₃—SiO₂) system and R₂O—Si₂O system (R═Li, Na, K) are describedin “Handbook of Glass Engineering” (ed. by M. Yamane et al., AsakuraSyoten, 1999, pp. 192), etc. and also selection or analogical selectionthereof will be possible from the following descriptions (a) to (f) in“Introduction to Ceramics”, 2nd edition, W. D. Kingery, H. K. Bowen, D.R. Uhlmann, John Wiley & Sons, Inc., 1975.

(a) Na₂B₈O₁₃—SiO₂ system (Na₂O.4B₂O₃—SiO₂ system) (pp. 113)

(b) RO—SiO₂ system (R═Mg, Ca, Sr, Ba, Fe, Zn) (pp. 118)

(c) R₂O—SiO₂ system (R═Li, Na, K) (pp. 119)

(d) BaO—Al₂O₃—SiO₂ system (pp. 120)

(e) Na₂O—B₂O₃—SiO₂ system (pp. 121)

(f) Na₂O—CaO—SiO₂ system (pp. 122)

The composition range of the separated-phase structure varies withtemperature and the range in two-component systems can be indicated froma diagram when a temperature is decided; however, there may be a case inwhich the range cannot be expressed in a three-component system such asNa₂O—B₂O₂—SiO₂ unless an end component is decided. For example, theabove-mentioned (a) is true of the case, that is, when the end componentis decided to be Na₂B₈O₁₃ and SiO₂, the diagram is expressed by the sameexpression as that of two-component systems; thus the range can bedecided from the diagram if the temperature is decided. Otherthree-component systems can be decided for their ranges by similarlydeciding their end components, etc.

If the transition metal ion cluster or transition metal cluster existsin the base glass as much as possible, warm color emission of yellow toorange is likely to generate; therefore, provided that emission ofyellow to orange in 550 to 650 nm (e.g. emission center: 580 nm) iswithin a level capable of visually confirming the emission of yellow toorange under excitation at 350 to 400 nm (e.g. 365 nm), e.g., underexcitation by a black light (central wavelength: 365 nm, 4 W), thenwhich demonstrates sufficient existence of the transition metal ioncluster or transition metal cluster.

Additionally, glass network-forming oxides such as P₂O₅, tin oxide (SnO)(acting also as a reducing agent during production), intermediate oxidessuch as Al₂O₂, TiO₂, ZnO, ZrO₂, Y₂O₃, PbO, and V₂O₅, for example, may beadded to the light-emitting glass of the present invention as a thirdcomponent in addition to the metal cluster or metal ion cluster and thebase glass described above. These third components may provideadvantages such as control of valence of the transition metal ion orsize of the separated-phase structure (separated-phase texture) byforming a glass network (skeleton) or modifying the glass networkdepending on the composition, etc. These third components may be usedalone or in combination of two or more.

(3) Production of Light-Emitting Glass:

The light-emitting glass of the present invention may be simply obtainedby mixing, e.g. dry-mixing etc., a raw material component which includescompounds in a predetermined compositional ratio correspondingly to thebase glass to form a separated-phase structure; a compound including thetransition metal corresponding to the transition metal ion cluster ortransition metal cluster, e.g. an oxide including the transition metal(copper oxide (I) (Cu₂O) or copper oxide (II) (CuO)), or coppercarbonate (CuCO₃), copper nitrate (Cu(NO₃)₂), copper sulfate (CuSO₄),copper chloride (I) (CuCl), copper chloride (II) (CuCl₂), etc. in caseswhere the transition metal is copper, or silver nitrate (AgNO₃), silveroxide (Ag₂O), etc. in cases where the transition metal is silver; andthe third component, etc. as required; and then vitrifying them byconventional glass production processes such as melting and quenchingprocesses (referred also as “glass ceramics process”); specifically, theraw material component is dry-mixed, then the raw material component isheated and melted and then maintained in a molten state, followed bybeing quenched; and if necessary, post-treatment such as processing intoa predetermined shape and polishing such as mirror-surface polishing maybe applied.

As the raw material of the base glass, lithium carbonate (Li₂CO₃),sodium carbonate (Na₂CO₃), or potassium carbonate (K₂CO₃), and boricacid (H₃BO₃) and silica (SiO₂) may be used in a case of alkali metalborosilicate glass (R₂O—B₂O₃—SiO₂), for example; and calcium carbonate(CaCO₃), magnesium carbonate (MgCO₃), strontium carbonate (SrCO₃), orbarium carbonate (BaCO₃), and boric acid (H₃BO₃) and silica (SiO₂) maybe used in a case of alkali earth metal borosilicate glass(R′O—B₂O₃—SiO₂), for example. Besides, desired one selected from lithiumcarbonate (Li₂CO₃), sodium carbonate (Na₂CO₃), potassium carbonate(K₂CO₃), calcium carbonate (CaCO₃), magnesium carbonate (MgCO₃),strontium carbonate (SrCO₃), and barium carbonate (BaCO₃), and boricacid (H₃BO₃) and silica (SiO₂) may be used in a case of alkalimetal-alkali earth metal borosilicate glass (R₂O—R′O—B₂O₃—SiO₂), forexample.

Lithium carbonate (Li₂CO₃), sodium carbonate (Na₂CO₃), or potassiumcarbonate (K₂CO₃) and silica (SiO₂) may be used in a case of alkalimetal silicate glass (R₂O—SiO₂), for example; and calcium carbonate(CaCO₃), magnesium carbonate (MgCO₃), strontium carbonate (SrCO₃), orbarium carbonate (BaCO₃) and silica (SiO₂) may be used in a case ofalkali metal silicate glass (R₂O—SiO₂), for example. Besides, desiredone selected from lithium carbonate (Li₂CO₃), sodium carbonate (Na₂CO₃),potassium carbonate (K₂CO₃), calcium carbonate (CaCO₃), magnesiumcarbonate (MgCO₃), strontium carbonate (SrCO₃), and barium carbonate(BaCO₃), and silica (SiO₂) may be used in a case of alkali metal-alkaliearth metal silicate glass (R₂O—R′O—SiO₂), for example.

Melting temperature (heating temperature) and melting time in themelting and quenching process may be appropriately set depending on thecomposition of the base glass, etc.; for example, the meltingtemperature (heating temperature) may be 1200° C. to 1700° C., and themelting time may be 0.5 to 2.0 hours.

The additive amount of the compound including the metal corresponding tothe transition metal ion cluster, etc. based on the base glass may beappropriately set depending on the composition of the base glass,species of the transition metal cluster, etc., and is preferablyappropriately set depending on the composition of the base glass, etc.within a range of about 0.01 to 2.0 mol % as outer percentage, forexample. When the additive amount is insufficient, the necessary amountof the metal ion cluster, etc. may not be formed within the base glass,and when the additive amount is excessive, unnecessary ions, colloids,etc. tend to form, thus the both cases may adversely affect the warmemission. It is particularly preferred that the additive amount of thecompound is appropriately set depending on the composition of the baseglass, etc. within a range of about 0.1 to 1.0 mol % as outerpercentage.

It is also necessary that the reduction condition of the transitionmetal ion, etc. is maintained in order to keep the valence of thetransition metal ion, etc. and effectively form the transition metal ioncluster or transition metal cluster of Cu⁺ cluster, etc.; and thus areducing agent is preferably added in order to maintain the reductioncondition of the transition metal ion, thereby the control of thereduction condition may be easily performed due to the addition of thereducing agent. Tin oxide (SnO), metal silicon (Si), sugars such assaccharose, starches such as dextrin, carbon powder, for example, may beused as the reducing agent; and tin oxide is preferably used from theviewpoint of ability thereof to selectively enter into a silica-poorglass phase and effectively promote the reduction even in a small amountthereof. Here, tin oxide exerts the function as the reducing agent dueto the change from Sn²⁺ to Sn⁴⁺ in the glass material.

In regards to the additive amount of the reducing agent, when tin oxideis used as the reducing agent, for example, an insufficient amount maymake it difficult to properly maintain the reduction condition, on theother hand, excessive addition thereof may adversely affect thestructure of the glass or crystallize the glass; therefore, the additiveamount may be appropriately set depending on species of the compoundused, composition of the base glass, desired emission intensity, etc.within a range of about 0.1 to 10.0 mol % as outer percentage, and theadditive amount is preferably 0.5 to 10.0 mol % and more preferably 0.5to 5.0 by mol %, particularly preferably, is set within a range of 1.0to 5.0 mol %.

Additionally, a reductive atmosphere may be formed by flowing nitrogengas or nitrogen-dilution hydrogen gas into heating furnaces such aselectric furnaces when forming the molten state, thereby the reductioncondition of the metal ion may be maintained after dry-mixing the rawmaterial component. Carbon monoxide (CO) gas may also be used instead ofthe nitrogen gas or nitrogen-dilution hydrogen for forming the reductiveatmosphere.

As described above, the borosilicate glass or silicate glass having aseparated-phase structure is used as the base glass in thelight-emitting glass of the present invention; therefore, the metal ioncluster or metal cluster emitting light of a warm white color (yellow toorange) when irradiated with near-ultraviolet light is effectively dopedin the base glass, and thus light-emitting glass phases, protectiveglass phases, and their boundaries to be centers of light scatter arecomplexified in a scale of micro to nano meter, thereby achieving toincrease excitation wavelength and emission wavelength and resulting ina fluorescent material which emits high-intensity light of a warm whitecolor (yellow to orange) upon irradiation with near ultraviolet lightdue to a multiple scattering effect. Furthermore, since the borosilicateor silicate glass, which is a common glass material, is employed as theconstituent material, it is possible to inexpensively provide afluorescent material combining long-term weatherability with respect toultraviolet rays, etc. with resistance to high temperatures.

As described above, the light-emitting glass of the present inventionuses the glass material having a separated-phase structure, then whichis doped with the transition metal ion clusters, etc., thereby resultingin the light-emitting glass with high-intensity due to the multiplescattering effect. The reason of increase in the emission intensity dueto the multiple scattering effect is that separated-phase textures proneto scatter near-ultraviolet of the excitation wavelength of several tento several hundred nm can be formed in the glass and irradiatedultraviolet light can be scattered several times by the separated-phasetextures to effectively excite metal ion clusters.

The light-emitting glass of the present invention may be combined with alight-emitting element to form a light-emitting source, and then whichmay be use as a light-emitting device. The light-emitting device emitshigh-intensity light of a warm white color (yellow to orange) and isexcellent in weatherability and heat resistance and thus may comply withsaving of energy in place of incandescent lights or fluorescent lampsand saving of rare resources.

The light-emitting element for forming the light-emitting device of thepresent invention is a photoelectric conversion element to convertelectric energy into light; specifically, light-emitting diodes such asultraviolet-visible light-emitting diodes, laser diodes,surface-emitting laser diodes, inorganic electroluminescence elements,organic electroluminescence elements, etc. may be used for thelight-emitting element; in particular, light-emitting diodes such asultraviolet-visible light-emitting diodes are preferable from theviewpoint of providing semiconductor light-emitting elements with highpower. The wavelength emitted by the light-emitting element as thelight-emitting source is not particularly limited in principle and of nomatter as long as it is within the range of wavelength capable ofexciting the light-emitting glass of the present invention; for example,the wavelength may be 330 to 450 nm.

The constitution of the light-emitting device of the present inventionis not particularly limited as long as the light-emitting glass of thepresent invention and the light-emitting element are used as alight-emitting source; for example, the light-emitting glass and thelight-emitting element are used as a light-emitting source, and thelight-emitting glass and the light-emitting element are constructed incombination such that the light-emitting glass covers the light-emittingelement. FIG. 2 is a schematic view showing an embodiment of thelight-emitting device of the present invention. In the light-emittingdevice 1 of the present invention shown in FIG. 2, the light-emittingglass 11 of the present invention and the light-emitting element 12consisting of light-emitting diodes, etc. are used as a light-emittingsource, and which is mounted on a submount element 14 while keepingconduction of the light-emitting element 12, thereby constructing thelight-emitting device 1 (semiconductor light-emitting element) withsealing the light-emitting element 12 by the package of thelight-emitting glass 11 of the present invention.

On the other hand, the embodiment described above is no more than oneembodiment of the present invention, thus the present invention is notlimited to the embodiment, and it is needless to say that modificationor improvement having the constitution of the present invention andwithin the range capable of achieving the purpose and effect of thepresent invention is encompassed by the present invention. Besides,specific structure, shape, etc. in carrying out the present inventionmay be changed uneventfully into other structure, shape, etc. within therange capable of achieving the purpose and effect of the presentinvention. The present invention is not limited to the illustrativeembodiments described above, and modification or improvement within therange capable of achieving the purpose of the present invention isencompassed by the present invention.

For example, the constitution of the light-emitting device 1 of thepresent invention shown in FIG. 2 is no more than one example, thelight-emitting device 1 is not limited to the constitution, and anyconstitution of the light-emitting source including the light-emittingglass 11 and the light-emitting element 12 may be employed.

For the rest, specific structure, shape, etc. in carrying out thepresent invention may be changed into other structure, etc. within therange capable of achieving the purpose of the present invention.

EXAMPLES

The present invention is explained more specifically with reference toExamples and Comparative Examples hereinafter; however, the presentinvention is not limited to Examples, etc. at all.

Examples 1 and 2 Preparation of Light-Emitting Glass Using Alkali MetalBorosilicate Glass

Two compositions, having a basic composition of Na₂O—B₂O₃—SiO₂ (NBSsystem) and considered to have a separated-phase structure in the phasediagram of FIG. 1, were selected for base glasses (base glass oflight-emitting glass in Example 1: 6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol %; baseglass of light-emitting glass in Example 2: 11.5Na₂O-44.0B₂O₃-44.5SiO₂mol %; expressed by encircled numbers 1 and 2 in order in FIG. 1).Additionally, additive amounts of copper oxide (Cu₂O) and species andadditive amounts of reducing agents are described in Evaluations below,in which the additive amounts are expressed by outer percentage.

An essential production process was such that sodium carbonate (Na₂CO₃),boric acid (H₃BO₃), and silica (SiO₂) were used as raw materials of thebase glasses and weighed in a desired mole ratio, then to which copperoxide (Cu₂O) and a reducing agent (tin oxide (SnO)) were added in adesired amount as outer percentage, followed by dry-mixing to obtain araw material component. The raw material component was put into analumina or platinum crucible and heated at 1500° C. for 30 to 60 minutesin an electric furnace to maintain a molten state, followed by beingquenched by flowing down a brass plate. The resulting coarse glass wasprocessed by a diamond cutter and a polishing device to prepare a glasssample of the light-emitting glass of the present invention.

Comparative Example 1

A mixed alkali borosilicate glass(15.0Na₂O-15.0K₂O-3.0Al₂O₃-17.0B₂O₃-50.0SiO₂ mol %) free from phaseseparation as a raw material of base glass and sodium carbonate(Na₂CO₃), potassium carbonate (K₂CO₃), alumina (Al₂O₃), boric acid(H₃BO₃), and (SiO₂) in a desired mole ratio were used to prepare a glasssample of a light-emitting glass of Comparative Example 1 using aprocess similar to the production process described above.

Evaluation (1) (Case of Selecting Tin Oxide as Reducing Agent):

FIG. 3 shows an absorption spectrum of the case (Example 1-A) where 0.16mol % of copper oxide (Cu₂O) was added on the basis of the compositionof Example 1 and 1.6 mol % of tin oxide (SnO) was added as a reducingagent. As shown in FIG. 3, an absorption end of ultraviolet side appearsat a position above 350 nm by adding tin oxide as a reducing agent,suggesting that there is absorption by copper ion cluster (Cu⁺ cluster)and tin oxide.

Furthermore, FIG. 4 shows appearance photographs of the cases whereExample 1-A was irradiated with white light or ultraviolet of centralwavelength 254 nm or 365 nm; and FIG. 5 shows an excitation spectrum andan emission spectrum thereof. As shown in FIG. 4, Example 1-A (additionof tin oxide) appears clear and colorless under irradiation with whitelight. Besides, Example 1-A exhibited very weak blue fluorescence underirradiation with ultraviolet light of 254 nm; and Example 1-A exhibitedalmost only yellow fluorescence under irradiation with ultraviolet lightof 365 nm.

These results also coincide with excitation and fluorescence spectra; asshown in FIG. 5, the glass sample of Example 1-A (addition of tin oxide)exhibited broad emission over an entire region of visible light of 400nm to 800 nm, which is considered as a mixture of blue emission due tocopper ion (Cu⁺) and yellow to orange emission due to copper ion cluster(Cu⁺ cluster); and it could be confirmed that emission in Example 1-A(addition of tin oxide) is mainly of yellow to orange emission due tocopper ion cluster (Cu⁺ cluster) since both of excitation spectrum andemission spectrum have shifted to longer wavelength side.

Evaluation (2) (Effect of Glass Composition):

Copper oxide of 0.5 mol % and tin oxide of 5.0 mol % as a reducing agentwere added to Na₂O—B₂O₃—SiO₂ base glass having a separated-phasestructure of Examples 1 and 2 or to a base glass not having aseparated-phase structure of Comparative Example 1, thereby preparingglass samples (referred to as Example 1, Example 2, and ComparativeExample 1 in order). In regards to the resulting glass samples, therelation between glass composition and absorption spectrum is shown inFIG. 6, appearance photographs of glass samples irradiated with whitelight or ultraviolet light of central wavelength 254 nm or 365 nm areshown in FIG. 7, and the relation between glass composition, excitationspectrum, and emission spectrum is shown in FIG. 8, respectively.

As shown in FIG. 6, increase in excitation wavelength and emissionwavelength was recognized for the glass samples of Examples 1 and 2which use an alkali metal borosilicate glass having a separated-phasestructure as the base glass compared to the glass sample of ComparativeExample 1 which uses the mixed alkali borosilicate system glass nothaving a separated-phase structure as the base glass. Besides, as shownin FIG. 7, all of the glass samples are transparent in terms ofappearance under white light irradiation. It could also be confirmedthat yellow emission is noticeable in the light-emitting glass samplesof Examples 1 and 2 under irradiation of ultraviolet light of 365 nm.

These results also coincide with the excitation and fluorescence spectrashown in FIG. 8, and all of the glass samples exhibited broad emissionover an entire region of visible light of 400 nm to 800 nm, but both ofexcitation spectra and emission spectra of the glass samples in Examples1 and 2 have shifted to longer wavelength side compared to those ofComparative Example 1. It could therefore be confirmed that emission inthe separated-phase glass samples of Examples 1 and 2 is mainly ofyellow to orange emission due to copper ion cluster (Cu⁺ cluster).

Evaluation (3) (Effect of Additive Amount of Copper Oxide Added):

Using the base glasses of Na₂O—B₂O₃—SiO₂ system having a separated-phasestructure in Examples 1 and 2, glass samples were prepared with settingthe additive amount of copper oxide (Cu₂O) to be 0.1, 0.3, and 0.5 mol %as outer percentage for Example 1 and 0.1, 0.3, 0.5, 1.0, and 1.5 mol %as outer percentage for Example 2. In addition, tin oxide (SnO) was usedas a reducing agent and added at 5.0 mol % as outer percentage.

The appearance photographs of the glass samples irradiated with whitelight or ultraviolet light of central wavelength 254 nm or 365 nm areshown in FIG. 9 (Example 1) and FIG. 10 (Example 2) in relation toadditive amounts of copper oxide added. As shown in FIGS. 9 and 10, itcould be confirmed that yellow emission becomes more intense as theadditive amount of copper oxide added is increased. Additionally, theglass sample of Example 1 at an additive amount of 0.5 mol % and theglass sample of Example 2 at an additive amount of 1.5 mol % exhibitedred coloration due to copper colloid (Cu colloid).

Furthermore, FIG. 11 shows a relation of an additive amount of copperoxide when wavelength intensity is 580 nm, considered to exhibit yellowemission, versus emission intensity (yellow emission intensity). Asshown in FIG. 11, the yellow emission intensity depends on the additiveamount of copper oxide added, and a maximum appeared at an additiveamount of about 0.2 mol % in the glass sample of Example 1 and at anadditive amount of about 0.3 mol % in the glass sample of Example 2. Itcould also be confirmed that the glass sample of Example 1 exhibitsyellow to orange emission of the same level as the glass sample ofExample 2 even in an addition of less amount of copper oxide (Cu⁺ ion).

Evaluation (4) (Effect of Species of Alkali Metal)

In this evaluation, three types of basic composition of base glass,considered to be within an area having a separated-phase structure, suchas of Example 1 (base glass of light-emission glass:6.6R₂O-28.3B₂O₃-65.1SiO₂ mol %), Example 2 (base glass of light-emissionglass: 11.5R₂O-44.0B₂O₃-44.5SiO₂ mol %), and Example 3 (base glass oflight-emission glass: 15.0R₂O-57.0B₂O₃-28.0SiO₂ mol %) were employed,lithium (Li) and potassium (K) were used in addition to sodium (Na) asalkali metal R, and an additive amount of 0.2 mol % of copper oxide andan additive amount of 5.0 mol % of tin oxide as a reducing agent wereadded for preparing light-emitting glass, thereby preparing 9 species ofglass samples.

When the resulting 9 species of glass samples were excited underirradiation by ultraviolet light of central wavelength 365 nm, all ofthe glass samples exhibited emission of yellow white to yellow emission,and blue emission could be confirmed in the case of excitation underirradiation by ultraviolet light of central wavelength 254 nm;therefore, it could be confirmed that both of copper ion (Cu⁺) andcopper ion cluster (Cu⁺ cluster) exist in the Li and K glass systemsalso similarly as the Na glass system and the latter is dominant.

Furthermore, with respect to the resulting 9 species of glass samples,fluorescence spectra under the excitation by near-ultraviolet light ofcentral wavelength 365 nm and excitation spectra using a maximumemission wavelength as a monitor wavelength are shown in FIG. 12(composition of Example 1), FIG. 13 (composition of Example 2), and FIG.14 (composition of Example 3), respectively.

As shown in FIGS. 12 to 14, all of the glass samples exhibited broademission over an entire region of visible light of 400 nm to 800 nmunder the excitation by near-ultraviolet light of central wavelength 365nm. By reason that the peak tops exist around 600 nm, it is consideredthat blue emission due to Cu⁺ and yellow to orange emission due tocopper ion cluster (Cu⁺ cluster) are combined also in the Li and K glasssystems similarly as the Na glass system and the latter is dominant. AsR₂O—B₂O₃ in their compositions increased, emission intensity becamelarger in the Li system, became smaller in the K system conversely, anddid not change notably in the Na system. It is also understood thatemission intensity becomes larger in the order of K, Na, and Li in termsof alkali metal species within the range of samples containing largerR₂O—B₂O₃ but it does not depend on the alkali metal species within therange of samples containing larger SiO₂.

Evaluation (5) (Effect of Additive Amount of Copper Oxide Added):

Using the base glass of Na₂O—B₂O₃—SiO₂ system having a separated-phasestructure of Example 1 (6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol %), glass sampleswere prepared with setting the additive amount of copper oxide (Cu₂O) tobe 0.1, 0.2, 0.3, 0.4, and 0.5 mol % as outer percentage. In addition,tin oxide (SnO) was used as a reducing agent and added at 5.0 mol % asouter percentage.

Then the glass samples of Example 1 were confirmed with respect tofluorescence spectra under the excitation by near-ultraviolet light ofwavelength 365 nm and fluorescence spectra under the excitation byultraviolet light of wavelength 254 nm versus the additive amount ofcopper oxide added. The results are shown in FIG. 15 (365 nm) and FIG.16 (254 nm). Besides, FIG. 17 is a graph showing a relation betweencopper oxide (Cu₂O) added and emission intensity. Additionally, valuesof peak top at about 600 nm in the case of central wavelength 365 nm andpeak top at about 470 nm in the case of central wavelength 254 nm wereemployed as the emission intensity (same in FIG. 22 below).

As the excitation by near-ultraviolet light of central wavelength 365 nmis shown by FIG. 15, broad emission over an entire region of visiblelight of 400 nm to 700 nm was wholly observed, peak tops existed around580 to 600 nm, and yellow to orange emission due to copper ion cluster(Cu⁺ cluster) could be confirmed. As shown in FIG. 17, the emissionintensity was almost stable when the additive amount of copper oxide(Cu₂O) was above 0.2 mol %.

Additionally, as the excitation of central wavelength 254 nm is shown byFIG. 16, similarly as those of 365 nm, broad emission over an entireregion of visible light of 400 nm to 700 nm was wholly observed, peaktops existed around 460 to 480 nm, and blue emission due to copper ion(Cu⁺) could be confirmed. As shown in FIG. 17, the emission intensitywas likely to somewhat decrease as the amount of copper oxide (Cu₂O)increased when the additive amount of copper oxide (Cu₂O) was above 0.2mol %.

Evaluation (6) (Investigation of Presence or Absence of Tin Oxide(SnO)):

Using the base glass of Na₂O—B₂O₃—SiO₂ system having a separated-phasestructure of Example 1 (6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol %), glass sampleswere prepared without adding tin oxide (SnO) of a reducing agent. Theadditive amount of copper oxide (Cu₂O) added as a source of transitionmetal ion cluster was 0.2 mol % as outer percentage. For reference, aglass sample was also prepared using the above-described composition ofthe base glass with setting the additive amount of tin oxide (SnO) to be5.0 mol % as outer percentage and the additive amount of copper oxide(Cu₂O) added as a source of transition metal ion cluster to be 0.2 mol %as outer percentage and evaluated together.

Then the glass sample prepared without adding tin oxide (SnO) and theglass sample with tin oxide (SnO) of 5.0 mol % as outer percentage andcopper oxide (Cu₂O) added as a source of transition metal ion cluster inthe additive amount of 0.2 mol % as outer percentage were confirmed withrespect to fluorescence spectra under the excitation by near-ultravioletlight of central wavelength 365 nm and fluorescence spectra under theexcitation by ultraviolet light of wavelength 254 nm. The results areshown in FIG. 18 (365 nm) and FIG. 19 (254 nm).

As shown in FIG. 18, under the excitation by near-ultraviolet light ofcentral wavelength 365 nm, yellow to orange emission due to copper ioncluster (Cu⁺ cluster) could be confirmed for the glass sample preparedwithout adding tin oxide (SnO) but the peak was small.

Additionally, under the excitation of central wavelength 254 nm as shownin FIG. 19, the glass sample without addition of tin oxide exhibitedbroad emission over an entire region of visible light of 400 nm to 700nm, a peak top existed around 460 to 480 nm, and blue emission due tocopper ion (Cu⁺) could be confirmed.

Evaluation (7) (Investigation of Additive Amount of Tin Oxide (SnO)):

Using the base glass of Na₂O—B₂O₃—SiO₂ system having a separated-phasestructure of Example 1 (6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol %), glass sampleswere prepared with setting the additive amount of tin oxide (SnO), usedas a reducing agent during production, to be 1.0, 3.0, 5.0, and 7.0 mol% as outer percentage. Here, the additive amount of copper oxide (Cu₂O)added as a source of transition metal ion cluster was 0.2 mol % as outerpercentage.

Then the glass samples of Example 1 prepared with changing the additiveamount of tin oxide added as a reducing agent during production wereconfirmed with respect to fluorescence spectra under the excitation bynear-ultraviolet light of central wavelength 365 nm and fluorescencespectra under the excitation by ultraviolet light of wavelength 254 nm.The results are shown in FIG. 20 (365 nm) and FIG. 21 (254 nm). Besides,FIG. 22 is a graph showing a relation between tin oxide (SnO) added andemission intensity.

As shown in FIG. 20, under the excitation by near-ultraviolet light ofcentral wavelength 365 nm, all of the glass samples added with tin oxideexhibited broad emission over an entire region of visible light of 400nm to 700 nm, peak tops existed around 580 to 600 nm, and yellow toorange emission due to copper ion cluster (Cu⁺ cluster) could beconfirmed. As shown in FIG. 22, as the additive amount of tin oxide wasincreased the emission intensity increased slightly.

Additionally, under the excitation of central wavelength 254 nm as shownin FIG. 21, similarly as those of 365 nm, broad emission over an entireregion of visible light of 400 nm to 700 nm was wholly observed, peaktops existed around 460 to 480 nm, and blue emission due to copper ion(Cu⁺) could be confirmed. As shown in FIG. 22, the emission intensitybecame smaller as the additive amount of tin oxide was increased.

Evaluation (8) (Relation with Transition Metal Ion Cluster):

Using the base glass of Na₂O—B₂O₃—SiO₂ system having a separated-phasestructure of Example 1 (6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol %), silver nitrate(AgNO₃; transition metal ion cluster: Ag⁺ ion cluster; “A” in FIGS. 23and 24 described later), manganese dioxide (MnO₂; transition metal ioncluster: Mn²⁺ ion cluster; “B”), silver oxide (Ag₂O; transition metalion cluster: Ag⁺ ion cluster; “C”), and chromium oxide (Cr₂O₃;transition metal ion cluster: Cr³⁺ ion cluster; “D”) were selected asthe species of the compound added as the source of the transition metalion cluster in place of copper oxide, thereby preparing glass samples.Here, the additive amount of the compounds added was 0.2 mol % as outerpercentage, and tin oxide (SnO) was used as a reducing agent and addedat 5.0 mol % as outer percentage.

Then the glass samples of Example 1 were confirmed with respect tofluorescence spectra under the excitation by near-ultraviolet light ofcentral wavelength 365 nm and fluorescence spectra under the excitationby ultraviolet light of wavelength 254 nm versus the species of thecompounds added as the source of the transition metal ion cluster. Theresults are shown in FIG. 23 (365 nm) and FIG. 24 (254 nm).

Under the excitation by near-ultraviolet light of central wavelength 365nm as shown in FIG. 23, glass samples, in which the transition metal ioncluster is Ag⁺ ion cluster by using silver nitrate (AgNO₂; transitionmetal ion cluster: Ag⁺) or silver oxide (Ag₂O; transition metal ioncluster: Ag⁺), exhibited broad emission over an entire region of visiblelight of 400 nm to 700 nm, and emission of 500 to 700 nm considered tobe yellow to orange emission due to silver ion cluster (Ag⁺ cluster)could be confirmed.

Additionally, under the excitation of central wavelength 254 nm as shownin FIG. 24, broad emission over an entire region of visible light of 400nm to 700 nm was observed, peak tops existed around 460 to 480 nm, andblue emission due to silver ion (Ag⁺), etc. could be confirmed.

Examples 3 to 5 Preparation of Light-Emitting Glass using Silicate Glass

Three compositions, having a basic composition of Na₂O—SiO₂ (NS system)and considered to have a separated-phase structure, were selected forbase glasses (base glass of light-emitting glass in Example 3:15.0Na₂O-85.0SiO₂ mol % (“E” in FIGS. 25 and 26 described later); baseglass of light-emitting glass in Example 4: 20.0Na₂O-80.0SiO₂ mol %(“F”); and base glass of light-emitting glass in Example 5:30.0Na₂O-70.0SiO₂ mol % (“G”)). Here, the additive amount of copperoxide (Cu₂O) added was 0.2 mol % as outer percentage, and tin oxide(SnO) of 5.0 mol % as outer percentage was used as a reducing agent.

An essential production process is such that sodium carbonate (Na₂CO₃)and silica (SiO₂) are used as raw materials of a base glass and weighedin a desired mole ratio, then to which copper oxide (Cu₂O) of 0.2 mol %as outer percentage and a reducing agent (tin oxide (SnO)) of 5.0 mol %as outer percentage were added, followed by dry-mixing to obtain a rawmaterial component. The raw material component was put into an aluminaor platinum crucible and heated at 1500° C. for 30 to 60 minutes in anelectric furnace to maintain a molten state, followed by being quenchedby flowing down like a brass plate. The resulting coarse glass wasprocessed by a diamond cutter and a polishing device to prepare a glasssample of the light-emitting glass of the present invention.

Evaluation (9) (Case of Silicate Glass as Base Glass):

The glass samples of Examples 3 to 5 were confirmed with respect tofluorescence spectra under the excitation by near-ultraviolet light ofcentral wavelength 365 nm and fluorescence spectra under the excitationby ultraviolet light of wavelength 254 nm. The results are shown in FIG.25 (365 nm) and FIG. 26 (254 nm). For reference, a glass sample (“H” inFIGS. 25 and 26), prepared from the above-described composition of thebase glass of Example 1 (6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol %) with addingcopper oxide (Cu₂O) of 0.2 mol % as outer percentage as a source oftransition metal ion cluster and tin oxide (SnO) of 0.2 mol % as outerpercentage as a reducing agent, was similarly evaluated.

As shown in FIG. 25, the glass samples of Examples 3 to 5 exhibitedbroad emission over an entire region of visible light of 400 nm to 700nm under the excitation by near-ultraviolet light of central wavelength365 nm. Yellow to orange emission due to copper ion cluster (Cu⁺cluster) could be confirmed, however, the peak top has sifted somewhatto the side of shorter wavelength compared to that of the base glasscomposition of 6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol % and slightly white-tingedyellow to orange emission was confirmed. The emission intensities becamemore intense as the content of Na₂O in the base glass increased (as thecontent of SiO₂ decreased).

Additionally, under the excitation of central wavelength 254 nm as shownin FIG. 26, similarly as those of 365 nm, broad emission over an entireregion of visible light of 400 nm to 700 nm was wholly observed. Blueemission due to copper ion (Cu⁺) could be confirmed, however, the peaktop has sifted somewhat to the side of longer wavelength compared tothat of the base glass composition of 6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol %and slightly white-tinged blue emission was confirmed. The emissionintensities became weaker as the content of Na₂O in the base glassincreased (as the content of SiO₂ decreased) and were wholly strongerthan that of the base glass composition of 6.6Na₂O-28.3B₂O₃-65.1SiO₂ mol%.

INDUSTRIAL APPLICABILITY

The present invention can be advantageously used as a technology toprovide a novel fluorescent material which emits high-intensity light ofa warm white color (yellow to orange) upon irradiation with nearultraviolet light, is exchangeable for incandescent lights orfluorescent lamps, and may comply with saving of energy and saving ofrare resources.

1. A light-emitting glass, comprising a borosilicate glass having aseparated-phase structure composed of at least one of (i) to (iii) belowas a base glass, wherein the base glass comprises a transition metal ioncluster and/or transition metal cluster containing at least one selectedfrom the group consisting of copper (Cu), gold (Au), and silver (Ag) asa constituent metal; (i) alkali metal borosilicate glass having aseparated-phase structure (R₂O—B₂O₃—SiO₂), (ii) alkali earth metalborosilicate glass having a separated-phase structure (R′O—B₂O₃—SiO₂),and (iii) alkali metal-alkali earth metal borosilicate glass having aseparated-phase structure (R₂O—R′O—B₂O₃—SiO₂); in (i) to (iii), Rrepresents an alkali metal and R′ represents an alkali earth metal,respectively.
 2. A light-emitting glass, comprising a silicate glasshaving a separated-phase structure composed of at least one of (iv) to(vi) below as a base glass, wherein the base glass comprises atransition metal ion cluster and/or transition metal cluster containingat least one selected from the group consisting of copper (Cu), gold(Au), and silver (Ag) as a constituent metal; (iv) alkali metal silicateglass having a separated-phase structure (R₂O—SiO₂), (v) alkali earthmetal silicate glass having a separated-phase structure (R′O—SiO₂), and(vi) alkali metal-alkali earth metal silicate glass having aseparated-phase structure (R₂O—R′O—SiO₂); in (iv) to (vi), R representsan alkali metal and R′ represents an alkali earth metal, respectively.3. The light-emitting glass according to claim 1, wherein the transitionmetal ion cluster is a copper ion cluster (Cu⁺ cluster), and the baseglass is an alkali metal borosilicate glass having a separated-phasestructure (R₂O—B₂O₃—SiO₂).
 4. The light-emitting glass according toclaim 3, wherein the alkali metal of the alkali metal borosilicate glassis sodium (Na).
 5. A light-emitting device, comprising thelight-emitting glass according to claim 1 and a light-emitting elementas a light-emitting source.
 6. The light-emitting device according toclaim 5, wherein the light-emitting element is a light-emitting diode.7. A process for producing the light-emitting glass according to claim1, comprising: dry-mixing a raw material component containing a compoundwhich corresponds to a borosilicate glass having a separated-phasestructure composed of at least one of (i) to (iii) for forming a baseglass and a compound containing a transition metal which corresponds tothe transition metal ion cluster and/or transition metal cluster,followed by melting and quenching thereof.
 8. A process for producingthe light-emitting glass according to claim 2, comprising: dry-mixing araw material component containing a compound which corresponds to asilicate glass having a separated-phase structure composed of at leastone of (iv) to (vi) for forming a base glass and a compound containing atransition metal which corresponds to the transition metal ion clusterand/or transition metal cluster, followed by melting and quenchingthereof.
 9. The process for producing the light-emitting glass accordingto claim 7, wherein tin oxide (SnO) is further included as a reducingagent.
 10. The process for producing the light-emitting glass accordingto claim 9, wherein an additive amount of the tin oxide (SnO) is 0.1 to10.0 mol % as outer percentage.
 11. A light-emitting device, comprisingthe light-emitting glass according to claim 2 and a light-emittingelement as a light-emitting source.
 12. The light-emitting deviceaccording to claim 11, wherein the light-emitting element is alight-emitting diode.
 13. A light-emitting device, comprising thelight-emitting glass according to claim 3 and a light-emitting elementas a light-emitting source.
 14. The light-emitting device according toclaim 13, wherein the light-emitting element is a light-emitting diode.15. A light-emitting device, comprising the light-emitting glassaccording to claim 4 and a light-emitting element as a light-emittingsource.
 16. The light-emitting device according to claim 15, wherein thelight-emitting element is a light-emitting diode.
 17. The process forproducing the light-emitting glass according to claim 8, wherein tinoxide (SnO) is further included as a reducing agent.
 18. The process forproducing the light-emitting glass according to claim 17, wherein anadditive amount of the tin oxide (SnO) is 0.1 to 10.0 mol % as outerpercentage.